High tension bushing



Jan. 16, 1940. R. M. EMBLIDGE.

HIGH TENSION BUSHING Filed Got. 12, 1936 m m MM Q Y o beri Patented Jan. 16, 1940 UNITED STATES PATENT OFFICE This invention relates to high tension bushings for circuit breakers and transformers and more particularly to high tension bushings provided with means for compensating for extremes of atmospheric conditions encountered in use by providing dielectric material to the bushing to prevent failure thereof. 7

In many instances circuit breakers intermediate high tension electrical feed lines or cables and a point of distribution and consumption of electrical' energy are located upon the exterior of buildings and are hence exposed to the extremes of temperature and weather conditions. This exposure with consequent heating and cooling of the bushing produces expansion and contraction of the component parts of the bushing and induces breathing throughthe seams with the possibility of introducing water containing electrolytes and the like with the result that the striking distance from the cable end to the ground connection may be reduced and should a short circuit result the heat vaporizes the inhaled moisture and expands the air, thus rupturing and shattering the bushing. In other circumstances the presence of moisture containing electrolytes, such as carbon dioxide, would offer a ready path for the current and so produce a failure of the bushing.

An object of the present invention is to provide an improved high tension bushing assembly of enhanced life and an assembly that eliminates the hazard produced by breathing.

In the drawing, Fig. 1 illustrates diagrammatically a circuit breaker assembled with bushings in accordance with the present invention.

Fig. 2 is an end elevation with certain parts in section of a circuit breaker provided with the device of the present invention. Fig. 3 is an enlarged view in section of a reservoir for liquid dielectric for attachment to a bushing and Fig. 4

is a bottom plan view of the reservoir shown in Fig. 3.

Referring more particularly to the drawing, l designates the oil tank or container of a high tension interrupter and I l designates a type of bushing of dielectric material such as porcelain, glass and the like, attached to oil tank l0 through the structure 12 in any well known fashion whereby one end of the bushing extends into tank II] to be united to a conducting cable.

In accordance with the invention, any well known or standard type of bushing adapted to contain dielectric packing may be used and for purposes of explaining the invention I have illustrated a specific type of bushing formed as a hollow cylindrical outer shell |5 of dielectric material such as porcelain and having a plurality of skirts or ribs [6 at spaced parallel intervals to increase the length of creepage surface or path for electric current. This shell 5 is secure- 6"- ly attached to structure 120i oil tank H] with a fluid tight connection and with cap It forms a chambered casing, the function of which will become apparent.

Within the chambered casing formed of cap ll 10 and insulator shell l5 and substantially axially thereof is a cable or plurality of conductors l8 protected by a covering of flexible sheet material It impregnated with a dielectric substance or substances, while the remainder of the chambered casing is filled with dielectric material which may be either or the liquid or solid type.

A ground connection is provided adjacent the bottom of shell l5 through the conducting element 2| of copper or other suitable material surm rounding the end of cable l8 and in contact with the flexible wrapping l9. Ground element 2| is formed with the spaced loop 22 having dielectric element 23 within the loop formed, for instance, of sheet material impregnated with dielectric oil.

Cap I1 is generally formed of metal and is fitted in fluid-tight fashion upon porcelain shell 15, generally with bolts (not shown) and a gasket. Contact member 2'! is interiorly threaded and engages the threaded end 24 of cable l8 and bears tightly against cap I! at the shouldered joint 28. A path for current from feed line 25 connected by nuts 26 to the exposed threaded end of contact member 2'! and cable I8, is thus provided. Sloping walls are between contact memher 21 and cap I! and form a chamber 29 for receiving oil, as later explained.

Attached at a point above porcelain shell l5 and, as illustrated, to cap I1, is a reservoir 30 having fluid communication to the interior of shell I5 through chamber 29.

Reservoir 30 comprises sight glass 3| assembled between upper casting 32 and lower casting Casting 32 is formed with an annular recess 33 upon the under side of the casting for 46 receiving the edge of sight glass 3| which bears against the gasket 34. Lower casting 35 is also formed with an annular recess 36 for receiving the lower edge of sight glass 3| against gasket 31. The upper and lower castings 32 and 35 and sight glass 3| are held in assembled relation by means of a plurality of bolts 38 extending through holes 39 in castings 32 and 35 and held tightly by means of nuts 40.

Lower casting member is formed with an in-- so i teriorly threaded nipple 4! adjacent annular recess 36 which extends to a substantial extent into the interior of reservoir '30 and through which fluid communication is made with chamber 29 and the interior of shell 15 through conduits 42 and 43 connected through the T 44.

Extending through the bottom casting 35 of reservoir 39 and adjacent to upper casting 32 is a breather pipe 45 through which air may enter and escape from the interior of the reservoir, as weatherconditions may causecontraction or expansion of dielectric 46 contained in the reservoir. The breather pipe may be attached in any fluid-tight fashion, as, for instance, by screwing the same through the casting or by means of ,a driving it as shown. Lower casting 35 is pro:

vided with an interiorly threaded hole 49 flush with the upper side of casting 35, and fitted with plug 41. As drain hole 49 is lower than the upper end 48 of nipple 4| a sump is provided" in which any water or other extraneous matter 50 of a gravity greater than the oil may collect.

, In assembling the improved circuit breaker of the present invention, oil reservoir 30 is attached to capl'i in such fashion that the jumping dis, tance is not decreased. This result is best ob away from the, vertical and thus form the sump,

defined by the top 48 of nipple 4| or'of the extension of conduit 42 into reservoir 30 with bottom plate 35 and sight glass 3! to collect electrolyte which mayform or be collected during service of the device.

What is claimed is:

A terminal insulated bushing for high tension electrical conductors comprising a hollow cylindrical casing of dielectric material, an electrical conductor within the casing and extending 00- H axially therewith, non-conducting material withend of said casing, a reservoir comprising a hollow transparent cylindrical portion disposed cylindrical portion and means for retaining said closure members in sealing relation with the ends of said transparent cylindrical portion, said closure cap containing a lateral port, a conduit communicating with the upper portion of said casingthrough said port and extending to and throughthe lower of said closure members to a point substantially above the upper face of said lower closure member to form a sump portion within said reservoir, pressure equalizing means comprising a tubular element disposed in said lower closure member and extending upwardly to a point adjacent the upper closure member and downwardly through the lower closure member to communicate with the atmosphere, and means in said lower closure member for draining the sump portion of said reservoir.

ROBERT M. EMBLIDGE. 

